JMeter is not smart enough to successfully replay recorded session as modern web applications use many ways of tracking the user, page he came from, status of web page, passing headers back and forth, etc.
JMeter can handle or workaround the majority of challenges, i.e. it provides =http://jmeter.apache.org/usermanual/component_reference.html#HTTP_Cookie_ManagerHTTP Cookie Manager to simulate user cookies and deal with cookie-based authentication,
HTTP Cache Manager to represent browser cache, etc.
However there could be some parameters, JMeter isn't able to handle automatically and some manual input will be required. If you see that your scripts are hitting only login page - something is definitely wrong. Take a look at
ASP.NET Login Testing with JMeter guide to learn how to work with dynamic parameters and perform their correlation.
I would also recommend familiarising yourself with
Using CSV DATA SET CONFIG guide to learn about basics of JMeter tests parametrization (if you planning to simulate 50 users you need to provide their credentials to the login request somehow)